Where Are They Now? Checking In On Four Cardiovascular Start-Ups

It's no secret increasing generic competition and regulatory oversight, combined with the financial challenges of developing a primary care drug, make cardiovascular a tough place for venture-backed biotechs. START-UP takes the pulse of four previously profiled cardiovascular companies -- arca Biopharma, Celladon, NovaCardia and Portola Pharmaceuticals, -- to see what lessons they've learned.